Process Of Water And Nitrogen Transport And Its Numerical Simulation Of Farmland In Mu Us Sandland

The research area in this paper is located in Nannitan Village,Bulanghe Township,Yulin City.The main crops are spring corn,The soil in the study area is mainly sandy with low water level and fertilizer holding capacity,and the nitrogen in the fertilizer is easily infiltrated into the soil and shallow groundwater with irrigation water and rainfall,which polluting the groundwater and affecting local farmers' drinking water safety and health.In this paper,the in-situ test,data analysis and HYDRUS-1D numerical simulation method are used to analyze the water and nitrogen migration in the study area.The HYDRUS-1D model was used to simulate the change of nitrate nitrogen content in the soil profile under different fertilization and irrigation amounts,and the leakage and leaching rate of nitrate nitrogen at the root and bottom of the model were calculated according to the model output file,with a view to providing a scientific basis for the control and sustainable development of local agricultural pollution.The main findings are as follows:(1)The overall water content of the study area increases with depth.The water content of shallow layers is more affected by rainfall and irrigation than deep layers.The soil water content of 10cm-20 cm fluctuates greatly with rainfall irrigation.The changes of soil water content at depths of 40 cm and 50 cm are closer to those of groundwater depth.There are hydraulically connected between groundwater and soil water.Correlation analysis show that the groundwater depth and the soil moisture content of each layer are negatively correlated,and the range of strong correlation with groundwater is 30cm-50 cm depth.(2)The nitrate nitrogen content of the 10 cm and 20 cm soil layers fluctuated greatly with rainfall irrigation and fertilization,and the nitrate nitrogen concentration in the 30-50 cm soil layer changed relatively smoothly,and was little affected by rainfall irrigation and fertilization.The leaching of nitrate nitrogen is closely related to rainfall and irrigation,and has a corresponding relationship with the leakage of soil water;(3)The concentration of nitrate nitrogen in different nitrogen application rates is T400>T300>T200>T100>CK in each soil layer,The concentration difference of nitrate nitrogen among the treatments gradually decreases with depth.The amount of nitrogen applied has an effect on the leaching loss of nitrate nitrogen but has a small effect.For every additional 100kg/ha of fertilization from CK to T400,In 2017,the cumulative nitrate nitrogen leaching loss at a depth of 50 cm increased by 8.44kg/ha,9.26kg/ha,7.71kg/ha,5.87kg/ha,respectively;In 2018,the cumulative nitrate nitrogen leaching loss at a depth of50 cm increased by 5.08kg/ha,4.35kg/ha,and 1.12kg/ha respectively.There is littledifference in the leaching loss of nitrate nitrogen between 90 cm and 150 cm soil layers with different nitrogen application rates.(4)The leaching loss of nitrate nitrogen is closely related to the amount of irrigation.The amount of irrigation has a greater influence on the leaching loss of nitrate nitrogen than the amount of nitrogen applied.The cumulative nitrate nitrogen leaching loss of each soil layer increased with the increase of irrigation amount,and the increase amount decreased with the increase of soil depth.Each increase of 10 mm in single irrigation,In 2017,the cumulative leaching loss of nitrate nitrogen at depths of 50 cm,90cm,and 150 cm was19.79kg/ha,14.17kg/ha,and 8.87kg/ha,respectively;In 2018,the cumulative leaching loss of nitrate nitrogen at the depths of 50 cm,90cm,and 150 cm was 15.03kg/ha,9.23kg/ha,and3.86kg/ha.